Despite the fact that it is taken for granted ubiquitously, flat glass processed to give window panes or auto glass is one of the most astonishing materials of our time. In contrast to hollow glass, it took several millennia longer until glass makers in the Middle Ages were able to produce flat glass panels that could be used for windows.
The most recent milestone in flat glass production was the development of the so-called float glass method in 1959. The novelty of the float method consists in the so-called “float ribbon”. This consists of molten tin. This tin bath is about 4 to 8 meters wide and up to 60 meters long. In this method, the liquid glass floats on the ideally flat liquid tin. When the glass mass is drawn from the melting furnace onto the tin bath, the tin is at a temperature of 1000° C. At the end of the tin bath, when the now solidified glass ribbon leaves the tin bath, the tin is at a temperature of 600° C. Tin is the only metal which satisfies the conditions required for this method: these are those of already being liquid at 600° C. and still not developing any disturbing vapor pressure at 1000° C.
After the solidified glass ribbon has been divided into the required formats after it has left the tin bath, the glass surfaces obtained in this way have to be stacked in order to be transported further.
U.S. Pat. No. 3,178,041 discloses a device for transporting successive plates, in which these plates, which move on a conveyor belt, are lifted up by means of a vacuum by a component fitted over the belt and are conveyed to one side of the belt via inclined conveying means. Likewise, plates are lifted up by means of a vacuum by a further component and are conveyed to the other side of the belt via inclined conveying means.
In this case, the prior art used as a basis here involves glass plates which transport workers grip with their hands by means of specific tools operating on the basis of vacuum technology and distribute onto both sides of a conveyor belt. Since this work constantly requires a number of workers, U.S. Pat. No. 3,178,041 was therefore based on the object of automating the desired operation.
This prior art merely characterizes the start of the development from the manual stacking of flat articles to mechanical processing of this object.
DE 199 35 665 A1, according to the details in claim 1, discloses a device for layering flat articles, in particular sheet metal panels, on top of one another at a plurality of stacking locations arranged behind one another. This device has a combined transport and depositing device which delivers the articles behind one another without any overlap with respect to one another, is designed as an overhead device, has a switchable article holding device and is intended for supplying the articles to the stacking locations, wherein a control device can be used to slow down the transport and depositing device from a transport speed to a depositing speed. It is also claimed that each article is deposited when or after the depositing speed has been reached, wherein the control device optionally carries out the braking operation with respect to one of the stacking locations or no braking is performed when the article is conveyed through at least one of the stacking locations and transported to the following or one of the following stacking locations and is braked and deposited there.
This device is based on the object of providing a device for stacking flat articles which makes precise and reproducible depositing possible with a high degree of flexibility and the greatest possible protection of the articles, operates quickly and precisely and has a small overall volume.
It is obviously not possible to use this known device for stacking glass plates.
In contrast, DE 10 2004 057 228 A1 discloses a method and a device for the high-speed stacking of plates, in particular glass plates, guided along a plate conveyor; this is based on the object of making it possible to stack plates of this type more quickly.
In order to achieve this object, it is claimed in the method as claimed in claim 1 that the respective plate is lifted up slightly from the plate conveyor at a stacking station by producing suction pressure on the upper side of the plate, is then gripped by frictional engagement or in some other way likewise on the upper side of the plate while retaining the suction pressure acting on the upper side of the plate, and is moved away from the plate conveyor to a position above a stacking table where it is deposited on the plate table by releasing the suction pressure and/or by mechanical pressure on the upper side of the plate counter to the action of the suction force, with the stacking table being lowered by the thickness of a plate after each plate has been deposited.
The method described in claim 1 of DE 10 2004 057 228 A1 and the device claimed in claim 2 essentially do not go beyond the prior art already described.
In addition, EP 1 666 386 A1 discloses a device and a method for orienting flat articles. This device is provided with two belts which run in parallel and can be operated at different speeds.
EP 1 498 370 A1 also discloses a device for transporting and rotating an article, said device having means which are intended to support the article, are arranged in a support plane and have longitudinal and rotational conveyors.
However, the devices in EP 1 666 386 A1 and EP 1 498 370 A1 are not suitable for stacking glass plates.
DE 43 38 981 C2 discloses a device for layering plates each having at least two defined guide holes, each plate being arranged at a predefined, oriented position.
However, an arrangement such as this is not suitable as a device for stacking glass plates.
Furthermore, DE 602 01 027 T2 discloses a device for handling and positioning separating elements in stacks of vertically arranged flat elements. Owing to the sensitivity of glass plates, this device is not suitable for stacking glass plates of different formats.